I agree with the conclusion, but do not think you can get their just by looking at how people would pay for a $400 emergency.
For example, in my financial situation, I would borrow to cover an unexpected $400 expanse. However, that is because I have a prior agreement with my parents that they would loan me (at 0% interest) to cover unexpected expenses, so I have no reason to keep a surplus of money fully liquid when it could be earning better returns elsewhere.
My parents, for their part, base their savings on the assumption that they would cover unexpected expanses from their line of credit secured against their house. This, again, is not because they do not have the money to set aside for emergencies, but because they think that the opportunity cost of keeping the money liquid outweighs the cost of occasionally paying on credit. As it happens, they could pay for a $400 emergency out of pocket, but that is mostly because they are too rich to micromanage at the $400 dollar level.
With respect to retirement savings, I do not think that stat is as bad as it first appears (although I do think the typical American is underrepresented for retirement). The basic financial story is:
1) take on debt for big, lifetime purchases (education and a house).
2) Pay of debt
3) Accumulate wealth
4) Retire and live off of accumulated wealth
Given this, it is not unreasonable that young people would have no money set aside for retirement, because it might be more efficient to use that money to pay off debt.